Introduction
Currently the distribution of tigers extends from the Pacific coast of Russia to West and Southern India, continuing East into the Malayan Peninsula and Sumatra. They inhabit a wide range of habitats from impenetrable tropical forest of Sumatra to the semi-arid tracts of Western India and the human dominated agricultural landscapes of the Gangetic Plains of India. The tiger (any sub-species) is always the top carnivore and the apex predator of any ecosystem wherever it is present. Being on top the food chain, they regulate the population of other predators, prey species (herbivores) and in turn the plant population of a forest. Apex predators are ones who have no natural predators of their own, and they reside at the top the food chain. The apex predator is at the highest trophic level and plays an important role in maintain the health of an ecosystem. Apex predators bring stability into prey-predator relationships when two prey species compete ecologically. Their role in an ecosystem percolating down the trophic levels is called trophic cascades.
The same is true for the Sumatran Tiger (Panthera tigris sumatrae). Unfortunately, the International Union for Conservation of Nature (IUCN) Red List of Threatened Species declares the Sumatran Tiger to be a “critically endangered” species. This has happened as an effect of habitat loss, illegal trade of body parts and depletion of prey numbers. Number of Sumatran tiger have reduced drastically over the last 15 years. So when the regulator of an ecosystem is affected, it effects the degree of ecosystem service it provides. Ecosystem service for the humans include soil nutrients provided by plants, pollination service by insects to help grow our crops, timber for wood, fossil fuels, contribution by forests to the water cycle, and many more. The “critically endangered” status of the Sumatran Tiger is because of its shrinking habitat and illegal trade in tiger parts resulting in poaching/ hunting.
The Sumatran Tiger and its habitat
According to a Government of Indonesia report in 2007, 51944 km2 protected forests forms the current home of the Sumatran tiger. This is just about half the earlier distribution of the species. These protected areas are namely: Bukit Barisan Selatan National Park, Batang Gadis National Park, Berbak National Park, Kerinci Seblat National Park, Gunung Leuser National Park, Way Kambas National Park, Bukit Tigapulu Tiger Conservation Landscape, Kermutan Tiger Conservation Landscape, Rimbang Baling Tiger Conservation Landscape, Tesso Nilo Tiger Conservation Landscape. Their estimated numbers in the wild range from 441-679. These areas occur as isolated patches interspersed by human dominated areas including agricultural areas and oil plantations. The habitat of the Sumatran Tiger is characterized by the presence of dense tropical evergreen forest and an elevation range of 0 to 3,200 meters. Bukit Barisan Selatan, Kerinci Seblat and the Gunung Leuser National Park forms the three sites that was declared Tropical Rainforest Heritage of Sumatra by UNESCO in 2004. The forests of Sumatran is home to about 10,000 species of plant, which includes 17 endemic genera. They have more than 200 species of mammals. 15 of the mammal species are endemic to the Indonesian region; like the endemic Sumatran orangutan. Of the 580 species of bird species 465 are resident pf Sumatra and 21 are endemic to the island. The wild species composition of the island provides biogeographic evidence of evolution.
All the year round the high mountain forests have a constant hot and humid temperature accompanied by rainfall for 9 months in wet areas and 7 months in drier areas. These areas receive a rainfall of 3000 mm to over 4000 mm, and the temperature ranges from 22 to 35°C. Humidity is always above 60%. This kind of a typical tropical climate is highly conducive for high speciation rates and species diversity. Droughts occur during El Niño Southern Oscillation (ENSO) events. Muntjac (Muntiacus muntjac), Sambar deer (Cervus unicolor), Malay tapir (Tapirus indicus), Mouse deer (Tragulus spp.), pigs (Sus scrofa), Pigtail macaques (Macaca nemestrina) and Argus pheasant (Argusianus argus) form the main prey of the Sumatran Tiger.,
Conservation threats
The most important threat that the Sumatran Tiger faces today are habitat destruction, hunting and depletion of prey numbers. Habitat destruction is caused by increase in agricultural areas and expansion of commercial plantations. More and more crops are needed to feed the growing population every day. So more forest areas are being cleared every day to make space for cultivation and human habitation. Commercial plantation in the form of palm oil plantation and Acacia plantations threaten the tiger habitat. The export of palm oil to international markets contributes a major amount of foreign exchange to the Sumatran economy. Forests are also cleared to provide timber for paper mills, which produces toilet paper which is then exported to the United States of America. Another significant threat is the human-tiger conflict. Loss of other sub-species of the tiger like the Bali Tiger and the Java tiger can be attributed to habitat loss and prey depletion caused by anthropogenic causes.
Roads cause fragmentation of forest patches into smaller fragments. Forests too close to public logging roads become more prone to human disturbance. From a source population, the Russian tiger population has been into a sink population just because of the effects of roads. In Sumatra, roads have been able to carry human disturbance deep into deep forests thereby reducing them into smaller, less self-sustaining habitat patches. Studies reveal that about 430 km of roads lie inside Sumatran forests, and they exposes about 16% of the total forest areas to human disturbance. Roads dissecting species rich forest patches act as barriers to the movement of animals. This creates isolated populations of animals, which may lead to extinction and less genetic variation due to inbreeding.
Human-tiger conflict occur when humans venture into the forest to gather timber, fodder or fuel wood. It also occurs when tiger, due to lack of prey in the forest, venture out into human dominated areas and prey on livestock. Humans as a retaliation poison the livestock kills to take revenge, and when tiger eat that kill they die. Such deaths resulting from retaliatory killings amount to 256. Crop depredation by large wild ungulates like pigs and various species of deer, which form the principle diet of the Sumatran Tigers, also pose a threat. When humans kill crop raiding ungulates, it depletes the wild prey population for the Sumatran Tiger. Hunting or poaching of tiger for body parts like skin, nails, teeth and bones for smuggling to Chinese markets, where it is used as traditional medicine, also poses a grave threat on the Sumatran Tiger population. A tiger skin in the local Sumatran market fetch $400 to $ 700. Hunting of prey species for meat and skin also indirectly affects the tigers. Between 1970and 1993 about 3990 kg of Sumatran Tiger bones were exported to Asian markets.
Conservation efforts invested
As a first response to the declining number of Sumatran Tigers the Ministry of Forestry in Sumatra in 1994 created the “Indonesian Sumatran Tiger Conservation Strategy” as a set of recommendations through the Directorate General of Forest Protection and Nature Conservation. The main aim of this was to ensure that the Sumatran tigers are able to sustain in their remaining range. The Indonesian Sumatran Tiger Conservation Strategy pledged to provide protection to the tigers and their habitat, to establish interactive management strategies for saving the disjunct wild population, to maintain captive populations as a stock, and to create awareness. All these efforts would then be carried ex-situ and in-situ to save the Sumatran Tiger.
In situ conservation is “conservation on-site”. It refers to protecting natural plant or animal species in their natural habitat like the forest. Ex-situ or “off-site conservation” refers to maintaining population of endangered or threatened plant or animal species away from their natural habitat, in places away from causes threatening its existence, like a zoo. These population serves a safe guard against extinction. This method is one of the oldest and the best known conservation techniques. Some recent developments like gene banks for various endangered species also form a part of ex-situ conservation methods.
As a result of all this planning, experts visited various Sumatran Zoos, where tigers were present, and the staff were trained on various aspect of ex-situ conservation of the Sumatran Tigers. Studbooks started to be maintained and genome banks were created. This ex-situ component was important because the zoo tigers will serve as a reserve in case the wild tigers become extinct. Once the ex-situ components were taken care of, the conservation strategy then focused on the in-situ components. It focused on studying the life-history characteristics and biology of wild Sumatran Tigers, studying how long term monitoring of these small tiger and prey populations can be done and resolution of human-tiger conflict in Sumatra. Various international cooperations with organizations in America, Europe, Asia and Australia were made.
Recently in 2010 the Ministry of Forestry of Indonesia have drafted the National Tiger Recovery Plan which targets to double the number of Sumatran Tiger by the year 2022 through scientific management and planning.
Conservation recommendations by current studies
Forest patches larger than 250 km2 where the tigers occur in Sumatra are very few in number and unprotected patches are smaller than 150m. These areas face a deforestation of 3.3% per year. This way these isolated patches become more and more cut off from one another with intensified human landuse creeping into them. The scientific research and management should in carried on in such a way so as to increase forest connectivity between these patches and to formulated land use policies accordingly. Certain studies have also shown selective logging in forests to be promoting abundance and diversity of prey species. Such scenarios, although may seem beneficial for the tiger, should be practiced with caution.
Study by Wibisono and Pusparini (2010) shows that the probability of occurrence of the Sumatran Tiger increases with distance from human indices disturbance like logging roads, factories, plantations and other infrastructure. These tigers also generally avoid high altitudes. So protecting the low land hill forests become imperative for the survival of the species. These forest are rich in prey species as well, which can support tiger populations. On the contrary, being more accessible than high altitudes, the low land hill forests are more prone to human alteration by land use change or by human disturbance in the form of extraction of various products from the forest and cattle grazing. Livestock should be stopped from grazing inside protected areas as they give competition for food resources to the wild ungulates, and a decrease in population of wild prey can in turn effect tiger numbers.
Research shows that in most places the forest department is under-staffed, which is an impediment in enforcing protection on ground. In such cases, involving the local communities in enforcing protection may prove helpful. This in turn, will also sensitize the local human population towards the conservation of Sumatran tigers. To win over the support of the local communities proper and adequate compensation schemes for loss of life and livestock should be put in place. Proper operating protocols have to be in place to deal with human tiger conflict.
The government in many places in Sumatra has developed a certain strategy for economic development that aims to raise generate revenue through Reducing Emissions from Deforestation and Forest Degradation (REDD) activities.
Finally, proper scientific methodologies should be in place to monitor the population, prey species, threats and challenges to conservation of the Sumatran Tiger on a regular and long term basis.
Conclusion
Instead of facing grave threats the Sumatran Tiger population still has potential for saving. There are various reasons for that. Enough amount of undisturbed forest habitats are still intact in Sumatra, and they strong conservation potential if managed properly. Luckily most of these patches have legal protection status. Most forests in Sumatra have higher forest guard to conservation area, then the global average. Substantial amount of scientific knowledge has been gathered about the species biology of the Sumatran tiger to effectively feed conservation efforts. Finally lot of enthusiastic conservationists have joined in the case of conserving the Sumatran Tiger. If the Ministry of Forest is to double the tiger numbers by 2022 as its long term strategic goal, they will have the follow the policies that was framed under the Indonesia-Norway Letter of Intent. These policies focus on merging a traditional protected area management system with innovative local solutions.
The status, threats and conservation issues faced by the Sumatran Tigers are no different from that faced by all tiger sub species present in the world. The scientific learning gathered from studying all the species is available to be applied to one another and to strengthen the conservation tiger as a whole. All said and done, whatever the recommendations be, the most important aspect of conserving a wild species is human attitude. The humans are amongst the most abundant life forms on earth and have the largest footprint. So if human population is to sustain on this planet we have to save whatever biota is left on this earth. After all, we are living of the cumulative savings of the ecosystem services that they have provided over millions of years before we came.
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